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Measuring waterwater pH

Q: We know that the pH of wastewaters is important if we want to release them in rivers, lakes or seas, etc. I want to know the best methods that measure the pH of wastewater in a lab.

A: The most accurate lab pH measurements use a hemispherical glass bulb and a fast reference electrode. The sample should be in a stirred, clean glass beaker at the same temperature as the process. Solution pH besides Nernst electrode temperature compensation should be used for process temperatures significantly different than 25ºC.

Here are more of the latest questions on: Instrumentation and Control

Can you explain a split range controller?
Regarding split range controller:

1. Is it normal to have a control valve with two different sizes?
2. Why use a split range controller and where can we it?
3. My application: I am planning to use at outlet of condenser. The outlet will have condensate liquid and non-condensate vapor. Will it work here?

Can you explain linearity and accuracy of flowmeters?
I am confused on linearity and accuracy of flowmeters such as oval meters. In some references they are mentioned as the same but in some others they are not the same. Should I only rely on linearity for selection for measuring custody transfer or another flowmeter characteristic?

Can you recommend a flowmeter?
We are going to install a flowmeter for lube oil loading as custody transfer. The flowrate may alter between 140-280 CMH (two-speed motor) having viscosity 150cSt at 40C. Simple installation and setting up on the line and reasonable cost as well as pressure drop are preferred. The pump can generate 8barg pressure. What would be the recommended flow measuring type to support the requested service?

Where should I install the control valve on the hot oil line?
I am going to use hot oil for heating a process in a jacketed vessel and I am going to make a control loop for controlling the vessel content. The hot oil enters at the bottom of the jacket and exits from the top. The control elements are RTD, controller, and control valve. My question: Where should I install the control valve on the hot oil line? Is it up stream or down stream of the vessel?

Why is there a discrepancy of solids at sampling points?
Ours is a fertilizer industry and within the premises we transfer phosphoric acid from the phosphoric acid production facility to the fertilizer production facility. The distance of the pipeline might be around 400m but the difference in issue and receipts generally comes out to be 100s of tons per day. Can you tell me what could be the possible problem? Other info required:

1. Phosphoric acid has around 5% solids
2. Sampling point in phosphoric acid tank is at the bottom
3. Sampling point in the fertilizer plant is at a higher level(25 ft) and is preceded by a lot of bends.

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